Method and device for maintaining the performance quality of a communication system in the presence of narrow band interference

ABSTRACT

A system that incorporates teachings of the subject disclosure may include, for example, a method for analyzing a wide frequency band with respect to signal power levels in specified narrow frequency bands, detecting narrow band signal power levels received in the specified narrow frequency bands, determining an average composite wideband power level from the narrow band signal power levels, determining an adaptive threshold from the average composite wideband power level, detecting narrow band interference according to the adaptive threshold, and configuring a filter to substantially suppress the detected narrow band interference. Other embodiments are disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/971,017, filed Jan. 8, 2008, which is a divisional of U.S.application Ser. No. 09/827,641, filed on Apr. 6, 2001, now U.S. Pat.No. 7,317,698, which is a continuation-in-part of U.S. patentapplication Ser. No. 09/301,477, filed on Apr. 28, 1999, now U.S. Pat.No. 6,807,405, which claims priority to Canadian Patent 2,260,653, filedFeb. 2, 1999. U.S. application Ser. No. 09/827,641, filed Apr. 6, 2001,now U.S. Pat. No. 7,317,698, also claims priority to U.S. ProvisionalApplication 60/195,387, filed Apr. 7, 2000. All sections of U.S. patentapplication Ser. No. 11/971,017 are incorporated herein by reference intheir entirety.

FIELD OF THE DISCLOSURE

The present invention is directed to communication systems and, moreparticularly, to a technique for detecting, identifying, extracting andeliminating narrowband interference in a wideband communication system.

BACKGROUND OF THE DISCLOSURE

As shown in FIG. 1, an exemplary telecommunication system 10 may includemobile units 12, 13, a number of base stations, two of which are shownin FIG. 1 at reference numerals 14 and 16, and a switching station 18 towhich each of the base stations 14, 16 may be interfaced. The basestations 14, 16 and the switching station 18 may be collectivelyreferred to as network infrastructure.

During operation, the mobile units 12, 13 exchange voice data or otherinformation with one of the base stations 14, 16, each of which areconnected to a conventional land line telephone network. For example,information, such as voice information, transferred from the mobile unit12 to one of the base stations 14, 16 is coupled from the base stationto the telephone network to thereby connect the mobile unit 12 with aland line telephone so that the land line telephone may receive thevoice information. Conversely, information, such as voice informationmay be transferred from a land line telephone to one of the basestations 14, 16, which, in turn, transfers the information to the mobileunit 12.

The mobile units 12, 13 and the base stations 14, 16 may exchangeinformation in either analog or digital format. For the purposes of thisdescription, it is assumed that the mobile unit 12 is a narrowbandanalog unit and that the mobile unit 13 is a wideband digital unit.Additionally, it is assumed that the base station 14 is a narrowbandanalog base station that communicates with the mobile unit 12 and thatthe base station 16 is a wideband digital base station that communicateswith the mobile unit 13.

Analog format communication takes place using narrowband 30 kilohertz(KHz) channels. The advanced mobile phone systems (AMPS) is one exampleof an analog communication system in which the mobile unit 12communicates with the base station 14 using narrowband channels.Alternatively, the mobile unit 13 communicates with the base stations 16using a form of digital communications such as, for example,code-division multiple access (CDMA) or time-division multiple access(TDMA). Digital communication takes place using spread spectrumtechniques that broadcast signals having wide bandwidths, such as, forexample, 1.25 megahertz (MHz) bandwidths.

The switching station 18 is generally responsible for coordinating theactivities of the base stations 14, 16 to ensure that the mobile units12, 13 are constantly in communication with the base station 14, 16 orwith some other base stations that are geographically dispersed. Forexample, the switching station 18 may coordinate communication handoffsof the mobile unit 12 between the base stations 14 and another analogbase station as the mobile unit 12 roams between geographical areas thatare covered by the two base stations.

One particular problem that may arise in the telecommunication system 10is when the mobile unit 12 or the base station 14, each of whichcommunicate using narrowband channels, interfere with the ability of thebase station 16 to receive and process wideband digital signals from thedigital mobile unit 13. In such a situation, the narrowband signaltransmitted from the mobile unit 12 or the base station 14 may interferewith the ability of the base station 16 to properly receive widebandcommunication signals.

SUMMARY OF THE INVENTION

According to one aspect, the present invention may be embodied in amethod of detecting and eliminating narrowband interference in awideband communication signal having a frequency bandwidth withnarrowband channels disposed therein. Such a method may include scanningat least some of the narrowband channels to determine signal strengthsin at least some of the narrowband channels and determining a thresholdbased on the signal strengths in at least some of the narrowbandchannels. Additionally, the method may include identifying narrowbandchannels having signal strengths exceeding the threshold and assigningfilters to at least some of the narrowband channels having signalstrengths exceeding the threshold. Furthermore, the method may includedetermining if the assigned filters are operating properly and bypassingany of the assigned filters that are not operating properly.

According to a second aspect, the present invention may be embodied in asystem adapted to detect and eliminate narrowband interference in awideband communication signal having a frequency bandwidth withnarrowband channels disposed therein. Such a system may include ascanner adapted to scan at least some of the narrowband channels todetermine signal strengths in at least some of the narrowband channels,a notch module adapted to receive the wideband communication signal andto selectively remove narrowband interference from the widebandcommunication signal to produce a filtered wideband communication signaland a bypass switch adapted to bypass the notch module when the bypassswitch is enabled. Furthermore, the system may include a controllercoupled to the scanner and to the notch module, wherein the controlleris adapted to determine a threshold based on the signal strengths in atleast some of the narrowband channels. Furthermore, the controller maybe adapted to identify narrowband channels having signal strengthsexceeding the threshold, to control the notch module to filter thewideband communication signal at a frequency corresponding to anarrowband channel having a signal strength exceeding the threshold, todetermine if the notch module is operating properly and to enable thebypass switch when the notch module is not operating properly.

According to a third aspect, the present invention may be embodied in amethod of detecting and eliminating narrowband interference in awideband communication signal having a frequency bandwidth withnarrowband channels disposed therein. Such a method may include scanningat least some of the narrowband channels to determine signal strengthsin at least some of the narrowband channels, determining a thresholdbased on the signal strengths in at least some of the narrowbandchannels and identifying fading narrowband channels having signalstrengths that do not exceed the threshold and that were previouslyidentified as exceeding the threshold, based on how long the identifiednarrowband channels have not exceeded the threshold. Additionally, themethod may include filtering the wideband communication signal at afrequency corresponding to a fading narrowband channel.

According to a fourth aspect, the present invention may be embodied in asystem adapted to detect and eliminate narrowband interference in awideband communication signal having a frequency bandwidth withnarrowband channels disposed therein. Such a system may include ascanner adapted to scan at least some of the narrowband channels todetermine signal strengths in at least some of the narrowband channelsin an order representative of a probability that the narrowband channelswill have interference and a notch module adapted to receive thewideband communication signal and to selectively remove narrowbandinterference from the wideband communication signal to produce afiltered wideband communication signal. The system may also include acontroller coupled to the scanner and to the notch module, wherein thecontroller is adapted to determining a threshold based on the signalstrengths in at least some of the narrowband channels. The controllermay be further adapted to identify fading narrowband channels havingsignal strengths that do not exceed the threshold and that werepreviously identified as exceeding the threshold, based on how long theidentified narrowband channels have not exceeded the threshold and tocontrol the notch module to filter the wideband communication signal ata frequency corresponding to a fading narrowband channel.

These and other features of the present invention will be apparent tothose of ordinary skill in the art in view of the description of thepreferred embodiments, which is made with reference to the drawings, abrief description of which is provided below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary illustration of a communication system;

FIG. 2 is an exemplary illustration of a base station of FIG. 1;

FIG. 3 is an exemplary illustration of a frequency spectrum of awideband signal in the absence of interference;

FIG. 4 is an exemplary illustration of a frequency spectrum of awideband signal in the presence of three narrowband interferers;

FIG. 5 is an exemplary illustration of a frequency spectrum of awideband signal having three narrowband interferers removed therefrom;

FIG. 6 is an exemplary illustration of one embodiment of an adaptivenotch filter (ANF) module of FIG. 2;

FIG. 7 is an exemplary illustration of a second embodiment of an ANFmodule of FIG. 2;

FIG. 8 is an exemplary illustration of a notch module of FIG. 7;

FIG. 9 is an exemplary illustration of a second embodiment of a notchfilter block of FIG. 8;

FIG. 10 is an exemplary flow diagram of a main routine executed by themicrocontroller of FIG. 7;

FIG. 11 is an exemplary flow diagram of a setup default values routineexecuted by the microcontroller of FIG. 7;

FIG. 12 is an exemplary flow diagram of a built in test equipment (BITE)test routine executed by the microcontroller of FIG. 7;

FIG. 13 is an exemplary flow diagram of a signal processing andinterference identification routine executed by the microcontroller ofFIG. 7;

FIG. 14 is an exemplary flow diagram of an interference extractionroutine executed by the microcontroller of FIG. 7;

FIG. 15 is an exemplary flow diagram of a fail condition check routineexecuted by the microcontroller of FIG. 7;

FIGS. 16A and 16B form an exemplary flow diagram of a main routineexecuted by the operations, alarms and metrics (OA&M) processor of FIG.7;

FIG. 17 is an exemplary flow diagram of a prepare response routineexecuted by the OA&M processor of FIG. 7; and

FIG. 18 is an exemplary flow diagram of a data buffer interrupt functionexecuted by the OA&M processor of FIG. 7.

DETAILED DESCRIPTION OF THE EMBODIMENTS

As disclosed in detail hereinafter, a system and/or a method fordetecting, identifying, extracting and reporting interference may beused in a communication system. In particular, such a system or methodmay be employed in a wideband communication system to protect against,or to report the presence of, narrowband interference, which hasdeleterious effects on the performance of the wideband communicationsystem.

As shown in FIG. 2, the signal reception path of the base station 16,which was described as receiving narrowband interference from the mobileunit 12 in conjunction with FIG. 1, includes an antenna 20 that providessignals to a low noise amplifier (LNA) 22. The output of the LNA 22 iscoupled to a splitter 24 that splits the signal from the LNA into anumber of different paths, one of which may be coupled to an adaptivenotch filter (ANF) module 26 and another of which may be coupled to anarrowband receiver 28. The output of the ANF module 26 is coupled to awideband receiver 30, which may, for example, be embodied in a CDMAreceiver or any other suitable wideband receiver. The narrowbandreceiver 28 may be embodied in a 15 KHz bandwidth receiver or in anyother suitable narrowband receiver. Although only one signal path isshown in FIG. 2, it will be readily understood to those having ordinaryskill in the art that such a signal path is merely exemplary and that,in reality, a base station may include two or more such signal pathsthat may be used to process main and diversity signals received by thebase station 16.

The outputs of the narrowband receiver 28 and the wideband receiver 30are coupled to other systems within the base station 16. Such systemsmay perform voice and/or data processing, call processing or any otherdesired function. Additionally, the ANF module 26 is alsocommunicatively coupled, via the Internet, telephone lines or any othersuitable media, to a reporting and control facility that is remote fromthe base station 16. In some networks, the reporting and controlfacility may be integrated with the switching station 18. The narrowbandreceiver 28 is communicatively coupled to the switching station 18 andmay respond to commands that the switching station 18 issues.

Each of the components 20-30 of the base station 16 shown in FIG. 2,except for the ANF module 26, may be found in a conventional widebandcellular base station, the details of which are well known to thosehaving ordinary skill in the art. It will also be appreciated by thosehaving ordinary skill in the art that FIG. 2 does not disclose everysystem or subsystem of the base station 16 and, rather, focuses on thesystems and subsystems of the base station 16 that are relevant to thedescription of the present invention. In particular, it will be readilyappreciated that, while not shown in FIG. 2, the base station 16includes a transmission system or subsystem.

During operation of the base station 16, the antenna 20 receiveswideband signals that are broadcast from the mobile unit 13 and couplessuch signals to the LNA 22, which amplifies the received signals andcouples the amplified signals to the splitter 24. The splitter 24 splitsthe amplified signal from the LNA 22 and essentially puts copies of theamplified signal on each of its output lines. The ANF module 26 receivesthe signal from the splitter 24 and, if necessary, filters the widebandsignal to remove any undesired narrowband interference and couples thefiltered wideband signal to the wideband receiver 30.

FIG. 3 illustrates a frequency spectrum 40 of a wideband signal that maybe received at the antenna 20, amplified and split by the LNA 22 and thesplitter 24 and coupled to the ANF module 26. If the wideband signalreceived at the antenna 20 has a frequency spectrum 40 as shown in FIG.3, the ANF module 26 will not filter the wideband signal and will simplycouple the wideband signal directly through the ANF module 26 to thewideband receiver 30.

However, as noted previously, it is possible that the wideband signaltransmitted by the mobile unit 13 and received by the antenna 20 has afrequency spectrum 42 as shown in FIG. 4. Such a frequency spectrum 42includes not only the wideband signal from the mobile unit 13 having afrequency spectrum similar to the frequency spectrum 40 of FIG. 3, butincludes three narrowband interferers 44, 46, 48, as shown in FIG. 4,one of which may be from the mobile unit 12. If a wideband signal havinga frequency spectrum 42 including narrowband interferers 44, 46, 48 isreceived by the antenna 20 and amplified, split and presented to the ANFmodule 26, the ANF module 26 will filter the frequency spectrum 42 toproduce a filtered frequency spectrum 50 as shown in FIG. 5.

The filtered frequency spectrum 50 has the narrowband interferers 44,46, 48 removed, therefore leaving a frequency spectrum 50 that is verysimilar to the frequency spectrum 40, which does not include anyinterference. The filtered wideband signal is then coupled from the ANFmodule 26 to the wideband receiver 30, so that the filtered widebandsignal spectrum 50 may be demodulated. Although some of the widebandsignal was removed during filtering by the ANF module 26, sufficientwideband signal remains to enable the wideband receiver 30 to recoverthe information that was broadcast by a mobile unit. Accordingly, ingeneral terms, the ANF module 26 selectively filters wideband signals toremove narrowband interference therefrom. Further detail regarding theANF module 26 and its operation is provided below in conjunction withFIGS. 6-17.

In general, one embodiment of an ANF module 60, as shown in FIG. 6,scans the frequency spectrum of the signal provided by the splitter 24and looks for narrowband interference therein. Such scanning may beimplemented by scanning to various known narrowband channels that existwithin the bandwidth of the wideband signal. For example, the ANF module60 may scan to various AMPS channels that lie within the bandwidth ofthe wideband signal. Alternatively, all of the frequency spectrumencompassed by the wideband signal may be scanned. Either way, whennarrowband interference is detected in the wideband signal, the ANFmodule 60 moves the narrowband interference into the notch of a notchfilter, thereby filtering the wideband signal to remove the narrowbandinterference.

In particular, as shown in FIG. 6, the signal from the splitter 24 iscoupled to a first mixer 62, which receives an additional input from avoltage controlled oscillator (VCO) 64. The first mixer 62 mixes thesignal from the splitter 26 with the signal from the VCO 64, therebyshifting the frequency spectrum of the signal from the splitter 24 andputting a portion of the shifted frequency spectrum located atintermediate frequency (IF) into a notch frequency of a notch filter 66.Accordingly, the component of the frequency shifted signal that is atthe IF is removed by the notch filter 66 having a notch frequency set atthe IF.

The resulting filtered signal is coupled from the notch filter 66 to asecond mixer 68, which is also driven by the VCO 64. The second mixer 68mixes the notch filter output with the signal from the VCO 64 to shiftthe frequency spectrum of the filtered signal back to an originalposition that the signal from the splitter 24 had. The output of thesecond mixer 68 is coupled to a band pass filter 70, which removes anyundesired image frequencies created by the second mixer 68.

In the system of FIG. 6, the narrowband interference present in thewideband signal is mixed to the IF, which is the notch frequency of thenotch filter 66, by the first mixer 62 and is, therefore, removed by thenotch filter 66. After the narrowband interference has been removed bythe notch filter 66, the second mixer 68 restores the signal to itsoriginal frequency position, except that the narrowband interference hasbeen removed. Collectively, the first mixer 62, the VCO 64, the notchfilter 66, the second mixer 68 and the band pass filter may be referredto as an “up, down filter” or a “down, up filter.”

The signal from the splitter 24 is also coupled to a bypass switch 72 sothat if no narrowband interference is detected in the wideband signalfrom the splitter 24, the bypass switch 72 may be enabled to bypass thenotch filter 66 and the mixers 62, 68, thereby passing the signal fromthe splitter 24 directly to the wideband receiver 30. Alternatively, ifnarrowband interference is detected, the bypass switch 72 is opened andthe signal from the splitter 24 is forced to go through the notch filter66.

To detect the presence of narrowband interference and to effectuatefrequency scanning, a number of components are provided. A discriminator74 receives the output signal from the first mixer 62 and detects signalstrength at the IF using a received signal strength indicator (RSSI)that is tuned to the IF. The RSSI output of the discriminator 74 iscoupled to a comparator 76, which also receives a threshold voltage on aline 78. When the RSSI signal from the discriminator 74 exceeds thethreshold voltage on the line 78, the comparator 76 indicates thatnarrowband interference is present at the IF, which is the notchfrequency of the notch filter 66. When narrowband interference isdetected, the sweeping action of the VCO 64 is stopped so that the notchfilter 66 can remove the interference at the IF.

To affect the sweeping action of the VCO 64, the output of thecomparator 76 is coupled to a sample and hold circuit 80, which receivesinput from a voltage sweep generator 82. Generally, when no interferenceis detected by the comparator 76, the output of the voltage sweepgenerator 82 passes through the sample and hold circuit 80 and isapplied to a summer 84, which also receives input from a low pass filter86 that is coupled to the output of the discriminator 74. The summer 84produces a signal that drives the VCO 64 in a closed loop manner. As thevoltage sweep generator 82 sweeps its output voltage over time, theoutput of the summer 84 also sweeps, which causes the frequency outputof the VCO 64 to sweep over time. The sweeping output of VCO 64, inconjunction with the discriminator 74 and the comparator 76, scan thesignal from the splitter 24 for interference. As long as the comparator76 indicates that narrowband interference is not present, the switch 72is held closed, because there is no need to filter the signal from thesplitter 24.

However, when the comparator 76 detects narrowband interference in thesignal from the splitter 24 (i.e., when the RSSI exceeds the voltage onthe line 78), the sample and hold circuit 80 samples the output of thevoltage sweep generator 82 and holds the sampled voltage level, therebyproviding a fixed voltage to the summer 84, which, in turn, provides afixed output voltage to the VCO 64. Because a fixed voltage is providedto the VCO 64, the frequency output by the VCO 64 does not change andthe signal from the splitter 24 is no longer scanned, but is frequencyshifted so that the narrowband interference is moved to the IF, which isthe notch frequency of the notch filter 66. Additionally, when thecomparator 76 indicates that narrowband interference is present, theswitch 72 opens and the only path for the signal from the splitter 24 totake is the path through the mixers 62, 68 and the notch filter 66.

The threshold voltage on the line 78 may be hand tuned or may begenerated by filtering some received signal strength. Either way, thevoltage on the line 78 should be set so that the comparator 76 does notindicate that interference is present when only a wideband signal, suchas the signal shown in FIG. 3, is present, but only indicatesinterference when a signal having narrowband interference is present.For example, the frequency spectrum 42 shown in FIG. 4, shows threenarrowband interferers 44, 46, 48, only one of the interferers would beneeded for the comparator 76 to indicate the presence of narrowbandinterference. As will be readily appreciated, the embodiment shown inFIG. 6 is only able to select and filter a single narrowband interfererwithin a wideband signal.

As shown in FIG. 7, a second embodiment of an ANF module 100, which mayfilter a number of narrowband interferers, generally includes a scanner102, an analog to digital converter (A/D) 104, a microcontroller 106, anoperations, alarms and metrics (OA&M) processor 108 and notch modules,two of which are shown in FIG. 7 at reference numerals 110 and 112. Themicrocontroller 106 and the OA&M processor 108 may be embodied in amodel PIC 16C77-20P microcontroller, which is manufactured by MicrochipTechnology, Inc., and a model 80386 processor, which is manufactured byIntel Corp., respectively. Although they are shown and described hereinas separate devices that execute separate software instructions, thosehaving ordinary skill in the art will readily appreciate that thefunctionality of the microcontroller 106 and the OA&M processor 108 maybe merged into a single processing device.

Additionally, the second embodiment of the ANF module 100 may include abuilt in test equipment (BITE) module 114 and a bypass switch 116, whichmay be embodied in a model AS239-12 gallium arsenide single-pole,double-throw switch available from Hittite. The microcontroller 106 andthe OA&M processor 108 may be coupled to external memories 118 and 120,respectively.

In general, the scanner 102, which includes a mixer 130, a discriminator132 and a programmable local oscillator 134, interacts with the A/D 104and the microcontroller 106 to detect the presence of narrowbandinterference in the signal provided by the splitter 24. The mixer 130and the programmable local oscillator 134 may be embodied in a modelMD-54-0005 mixer available from M/A-Com and a model AD9831 directdigital synthesizer, which is manufactured by Analog Devices, Inc.,respectively. Additionally, the A/D 104 may be completely integratedwithin the microcontroller 106 or may be a stand alone device coupledthereto.

As described in further detail below, once narrowband interference isdetected in the signal from the splitter 24, the microcontroller 106,via serial bus 136, controls the notch modules 110, 112 to remove thedetected narrowband interference. Although the second embodiment of theANF module 100, as shown in FIG. 7, includes two notch modules 110, 112,additional notch modules may be provided in the ANF module 100. Thenumber of notch modules that may be used in the ANF module 100 is onlylimited by the signal degradation that each notch module contributes.Because multiple notch modules are provided, multiple narrowbandinterferers may be removed from the wideband signal from the splitter24. For example, if three notch modules were provided, a wideband signalhaving the frequency spectrum 42, as shown in FIG. 4, may be processesby the ANF module 110 to produce a filtered wideband signal having thefrequency spectrum 50, as shown in FIG. 5.

The scanner 102 performs its function as follows. The signal from thesplitter 24 is coupled to the mixer 130, which receives an input fromthe programmable local oscillator 134. The mixer 130 mixes the signalsfrom the splitter 24 down to an IF, which is the frequency that thediscriminator 132 analyses to produce an RSSI measurement that iscoupled to the A/D 104. The A/D 104 converts the RSSI signal from ananalog signal into a digital signal that may be processed by themicrocontroller 106. The microcontroller 106 compares the output of theA/D 104 to an adaptive threshold that the microcontroller 106 haspreviously determined. Details regarding how the microcontroller 106determines the adaptive threshold are provided hereinafter. If themicrocontroller 106 determines that the output from the A/D 104, whichrepresents RSSI, exceeds the adaptive threshold, one of the notchmodules 110, 112 may be assigned to filter the signal from the splitter24 at the IF having an RSSI that exceeds the adaptive threshold.

The microcontroller 106 also programs the programmable local oscillator134 so that the mixer 130 moves various portions of the frequencyspectrum of the signal from the splitter 24 to the IF that thediscriminator 132 processes. For example, if there are 59 narrowbandchannels that lie within the frequency band of a particular widebandchannel, the microcontroller 106 will sequentially program theprogrammable local oscillator 134 so that each of the 59 channels issequentially mixed down to the IF by the mixer 132 so that thediscriminator 132 can produce RSSI measurements for each channel.Accordingly, the microcontroller 106 uses the programmable localoscillator 134, the mixer 130 and the discriminator 132 to analyze thesignal strengths in each of the 60 narrowband channels lying within thefrequency band of the wideband signal. By analyzing each of the channelsthat lie within the frequency band of the wideband signal, themicrocontroller 106 can determine an adaptive threshold and candetermine whether narrowband interference is present in one or more ofthe narrowband channels.

Once channels having narrowband interference are identified, themicrocontroller 106 may program the notch modules 110, 112 to remove themost damaging interferers, which may, for example, be the strongestinterferers. As described in detail hereinafter, the microcontroller 106may also store lists of channels having interferers, as well as variousother parameters. Such a list may be transferred to the reporting andcontrol facility or a base station, via the OA&M processor 108, and maybe used for system diagnostic purposes.

Diagnostic purposes may include, but are not limited to, controlling thenarrowband receiver 28 to obtain particular information relating to aninterferer and retasking the interferer by communicating with its basestation. For example, the reporting and control facility may use thenarrowband receiver 28 to determine the identity of an interferer, suchas a mobile unit, by intercepting the electronic serial number (ESN) ofthe mobile unit, which is sent when the mobile unit transmitsinformation on the narrowband channel. Knowing the identity of theinterferer, the reporting and control facility may contactinfrastructure that is communicating with the mobile unit and mayrequest the infrastructure to change the transmit frequency of themobile unit (i.e., the frequency of the narrowband channel on which themobile unit is transmitting) or may request the infrastructure to dropcommunications with the interfering mobile unit all together.

Additionally, diagnostic purposes may include using the narrowbandreceiver 28 to determine a telephone number that the mobile unit isattempting to contact and, optionally handling the call. For example,the reporting and control facility may use the narrowband receiver 28 todetermine that the user of the mobile unit was dialing 911, or any otheremergency number, and may, therefore, decide that the narrowbandreceiver 28 should be used to handle the emergency call by routing theoutput of the narrowband receiver 28 to a telephone network.

FIG. 8 reveals further detail of one of the notch modules 110, it beingunderstood that any other notch modules used in the ANF module 100 maybe substantially identical to the notch module 110. In general, thenotch module 110 is an up, down or down, up filter having operationalprinciples similar to the ANF module 60 described in conjunction withFIG. 6. In particular, the notch module 110 includes first and secondmixers 150, 152, each of which receives an input signal from a phaselocked loop (PLL) 154 that is interfaced through a logic block 156 tothe serial bus 136 of the microcontroller 106. Disposed between themixers 150, 152 is a notch filter block 158, further detail of which isdescribed below. In practice, the mixers 150, 152 may be embodied inmodel MD54-0005 mixers that are available from M/A-Com and the PLL 154may be embodied in a model LMX2316™ frequency synthesizer that iscommercially available from National Semiconductor.

During operation of the ANF module 100, the microcontroller 106 controlsthe PLL 154 to produce an output signal that causes the first mixer 150to shift the frequency spectrum of the signal from the splitter 24 to anIF, which is the notch frequency of the notch filter block 158.Alternatively, in the case of cascaded notch modules, the notch modulemay receive its input from another notch module and not from thesplitter 24. The output of the PLL 154 is also coupled to the secondmixer to shift the frequency spectrum of the signal from the notchfilter block 158 back to its original position as it was received fromthe splitter 24 after the notch filter block 158 has removed narrowbandinterference therefrom. The output of the second mixer 152 is furthercoupled to a filter 160 to remove any undesired image frequencies thatmay be produced by the second mixer 152. The output of the filter 160may be coupled to an additional notch module (e.g., the notch module112) or, if no additional notch modules are used, may be coupleddirectly to the wideband receiver 30.

Additionally, the notch module 110 includes a bypass switch 164 that maybe used to bypass the notch module 110 in cases where there is nonarrowband interference to be filtered or in the case of a notch module110 failure. For example, the microcontroller 106 closes the bypassswitch 164 when no interference is detected for which the notch module110 is used to filter. Conversely, the microcontroller 106 opens thebypass switch 164 when interference is detected and the notch module 110is to be used to filter such interference.

As shown in FIG. 8, the notch filter block 158 includes a filter 165,which may be, for example a filter having a reject band that isapproximately 15 KHz wide at −40 dB. The reject band of the filter 165may be fixed at, for example, a center frequency of 150 MHz or at anyother suitable frequency at which the IF of the mixer 150 is located.

Although the notch filter block 158 of FIG. 8 shows only a single filter165, as shown in FIG. 9, a second embodiment of a notch filter block 166may include a switch 170 and multiple filters 172-178. In such anarrangement, each of the filters 172-178 has a notch frequency tuned tothe IF produced by the first mixer 150. Additionally, each of thefilters 172-178 may have a different reject bandwidth at −40 dB. Forexample, as shown in FIG. 9, the filters 172-178 have reject bandwidthsof 15 KHz to 120 KHz. The use of filters having various rejectbandwidths enables the ANF module 100 to select a filter having anoptimal reject bandwidth to best filter an interferer.

During operation, of the second embodiment of the notch filter block166, the microcontroller 106 controls the switch 170 to route the outputsignal from the first mixer 150 to one of the filters 172-178. Themicrocontroller 106, via the switch 170, selects the filter 172-178having a notch switch best suited to filter interference detected by themicrocontroller 106. For example, if the microcontroller 106 determinesthat there is interference on a number of contiguous channels, themicrocontroller 106 may use a filter 172-178 having a notch width wideenough to filter all such interference, as opposed to using a singlefilters to filter interference on each individual channel. Additionally,a single filter having a wide bandwidth may be used when two narrowbandchannels having interference are separated by a narrowband channel thatdoes not have narrowband interference. Although the use of a single widebandwidth filter will filter a narrowband channel not havinginterference thereon, the wideband signal information that is lost isnegligible.

Having described the detail of the hardware aspects of the system,attention is now turned to the software aspects of the system. Ofcourse, it will be readily understood by those having ordinary skill inthe art that software functions may be readily fashioned into hardwaredevices such as, for example, application specific integrated circuits(ASICs). Accordingly, while the following description pertains tosoftware, such a description is merely exemplary and should not beconsidered limiting in any way.

That being said, FIGS. 10-15 include a number of blocks representativeof software or hardware functions or routines. If such blocks representsoftware functions, instructions embodying the functions may be writtenas routines in a high level language such as, for example, C, or anyother suitable high level language, and may be compiled into a machinereadable format. Alternatively, instructions representative of theblocks may be written in assembly code or in any other suitablelanguage. Such instructions may be stored within the microcontroller 106or may be stored within the external memory 118 and may be recalledtherefrom for execution by the microcontroller 106.

A main routine 200, as shown in FIG. 10, includes a number of blocks orroutines that are described at a high level in connection with FIG. 10and are described in detail with respect to FIGS. 11-15. The mainroutine 200 begins execution at a block 202 at which the microcontroller102 sets up default values and prepares to carry out the functionalityof the ANF module 100. After the setup default values function iscomplete, control passes to a block 204, which performs a built-in testequipment (BITE) test of the ANF module 100.

After the BITE test has been completed, control passes from the block204 to a block 206, which performs signal processing and interferenceidentification. After the interference has been identified at the block206, control passes to a block 208 where the identified interference isextracted from the wideband signal received by the ANF module 100.

After the interference has been extracted at the block 208, controlpasses to a block 210 at which a fail condition check is carried out.The fail condition check is used to ensure that the ANF module 100 isoperating in a proper manner by checking for gross failures of the ANFmodule 100.

After the fail condition check completes, control passes from the block210 to a block 212, which performs interference data preparation thatconsists of passing information produced by some of the blocks 202-210from the microcontroller 106 to the OA&M 108. Upon completion of theinterference data preparation, the main routine 200 ends its execution.The main routine 200 may be executed by the microcontroller 106 at timeintervals such as, for example, every 20 MS.

As shown in FIG. 11, the setup default values routine 202 beginsexecution at a block 220 at which the microcontroller 106 tunes theprogrammable local oscillator 134 to scan for interference on a firstchannel designated as F1. For example, as shown in FIG. 11, F1 may be836.52 megahertz (MHz). Alternatively, as will be readily appreciated bythose having ordinary skill in the art, the first channel to which theANF module 100 is tuned may be any suitable frequency that lies withinthe frequency band or guard band of a wideband channel.

After the microcontroller 106 is set up to scan for interference on afirst frequency, control passes from the block 220 to a block 222, whichsets up default signal to noise thresholds that are used to determinethe presence of narrowband interference in wideband signals receivedfrom the splitter 24 of FIG. 2. Although subsequent description willprovide detail on how adaptive thresholds are generated, the block 222merely sets up an initial threshold for determining presence ofnarrowband interference.

After the default thresholds have been set at the block 222 controlpasses to a block 224 at which the microcontroller 106 reads variousinputs, establishes serial communication with the notch modules 110, 112and any other serial communication devices, as well as establishescommunications with the OA&M processor 108. After the block 224completes execution, the setup default values routine 202 returnscontrol to the main program and the block 204 is executed.

FIG. 12 reveals further detail of the BITE test routine 204, whichbegins execution after the routine 202 completes. In particular, theBITE test routine 204 begins execution at a block 240, at which themicrocontroller 106 puts the notch modules 110, 112 in a bypass mode byclosing their bypass switches 190. After the notch modules 110, 112 havebeen bypassed, the microcontroller 106 programs the BITE module 114 togenerate interferers that will be used to test the effectiveness of thenotch modules 110, 112 for diagnostic purposes. After the notch modules110, 112 have been bypassed and the BITE module 114 is enabled, controlpasses from the block 240 to a block 242.

At the block 242, the microcontroller 106 reads interferer signal levelsat the output of the notch module 112 via the A/D 104. Because the notchmodules 110, 112 have been bypassed by the block 240, the signal levelsat the output of the notch module 112 should include the interferencethat is produced by the BITE module 114.

After the interferer signal levels have been read at the block 242, ablock 244 determines whether the read interferer levels are appropriate.Because the notch modules 110, 112 have been placed in bypass mode bythe block 240, the microcontroller 106 expects to see interferers at theoutput of the notch module 112. If the levels of the interferer detectedat the output of the notch module 112 are not acceptable (i.e., are toohigh or too low), control passes from the block 244 to a block 246 wherea system error is declared. Declaration of a system error may includethe microcontroller 106 informing the OA&M processor 108 of the systemerror. The OA&M processor 108, in turn, may report the system error to areporting and control facility. Additionally, declaration of a systemerror may include writing the fact that a system error occurred into theexternal memory 118 of the microcontroller 106.

Alternatively, if the block 244 determines that the interferer levelsare appropriate, control passes from the block 244 to a block 248 atwhich the microcontroller 106 applies one or more of the notch modules,110, 112. After the notch modules 110, 112 have been applied (i.e., notbypassed) by the block 248, control passes to a block 250, which readsthe signal level at the output of the notch module 112. Because the BITEmodule 114 produces interference at frequencies to which the notchfilters are applied by the block 248, it is expected that the notchmodules 110, 112 remove such interference.

After the signal levels are read by the block 250, control passes to ablock 252, which determines if interference is present. If interferenceis present, control passes from the block 252 to the block 246 and asystem error is declared because one or more of the notch modules 110,112 are not functioning properly because the notch modules 110, 112should be suppressing the interference generated by the BITE module 114.Alternatively, if no interference is detected at the block 252, the ANFmodule 100 is functioning properly and is, therefore, set to a normalmode of operation at a block 254. After the block 254 or the block 246have been executed, the BITE test routine 204 returns control to themain program 200, which begins executing the block 206.

As shown in FIG. 13, the signal processing and interferenceidentification routine 206 begins execution at a block 270. At the block270, the microprocessor 106 controls the programmable local oscillator134 so that the microcontroller 106 can read signal strength values foreach of the desired channels via the discriminator 132 and the A/D 104.In particular, the microcontroller 106 may control the programmablelocal oscillator 134 to tune sequentially to a number of known channels.The tuning moves each of the known channels to the IF so that thediscriminator 132 can make an RSSI reading of the signal strength ofeach channel. Optionally, if certain channels have a higher probabilityof having interference than other channels, the channels having thehigher probability may be scanned first. Channels may be determined tohave a higher probability of having interference based on historicalinterference patters or interference data observed by the ANF module100.

Additionally, at the block 270, the microcontroller 106 controls theprogrammable local oscillator 134 to frequency shift portions of theguard bands to the IF so that the discriminator 132 can produce RSSImeasurements of the guard bands. Because the guard bands are outside ofa frequency response of a filter disposed within the wideband receiver30, the block 270 compensates guard band signal strength reading byreducing the values of such readings by the amount that the guard bandswill be attenuated by a receiver filter within the wideband receiver 30.Compensation is carried out because the ANF module 100 is concerned withthe deleterious effect of narrowband signals on the wideband receiver30. Accordingly, signals having frequencies that lie within the passbandof the filter of the wideband receiver 30 do not need to be compensatedand signals falling within the guard band that will be filtered by thereceive filter of the wideband receiver 30 need to be compensated.Essentially, the guard band compensation has a frequency response thatis the same as the frequency response of the wideband receiver filter.For example, if a wideband receiver filter would attenuate a particularfrequency by 10 dB, the readings of guard bands at that particularfrequency would be attenuated by 10 dB.

After the block 270 is completed, control passes to a block 272, whichselects a number of channels having the highest signal levels. Commonly,the number of channels that will be selected by the block 272corresponds directly to the number of notch modules, 110, 112 that areemployed by a particular ANF module 100. After the channels having thehighest signal levels are selected by the block 272, control passes fromthe block 272 to a block 274.

At the block 274, the microcontroller 106 determines an adaptivethreshold by calculating an average signal strength value for thedesired channels read by the block 270. However, the average iscalculated without considering the channels having the highest signallevels that were selected by the block 272. Alternatively, it would bepossible to calculate the average by including the signal levelsselected by the block 272. The block 274 calculates an average that willbe compensated by an offset and used to determine whether narrowbandinterference is present on any of the desired channels read by the block270.

After the block 274 completes execution control passes to a block 276,which compares the signal strength values of the channels selected bythe block 272 to the adaptive threshold, which is the sum of the averagecalculated by the block 274 threshold and an offset. If the selectedchannels from the block 272 have signal strengths that exceeds theadaptive threshold, control passes to a block 278.

The block 278 indicates the channels on which interference is presentbased on the channels that exceeded the adaptive threshold. Such anindication may be made by, for example, writing information from themicrocontroller 106 to the external memory 118, which is passed to theOA&M processor 108. After the interferers have been indicated by theblock 278, control passes to a block 280. Additionally, if none of thechannels selected by the block 272 have signal strengths that exceed theadaptive threshold, control passes from the block 276 to the block 280.

At the block 280, the microcontroller 106 updates an interference datato indicate on which channels interferers were present. In particular,each frame (e.g., 20 ms) the microcontroller 106 detects interferers bycomparing power levels (RSSI) on a number of channels to the thresholdlevel. When an inteferer is detected, data for that interferer iscollected for the entire time that the interferer is classified as aninterferer (i.e., until the RSSI level of the channel falls below thethreshold for a sufficient period of time to pass the hang time testthat is described below). All of this information is written to a memory(e.g., the memory 118 or 120), to which the OA&M processor 108 hasaccess. As described below, the OA&M processor 108 processes thisinformation to produce the interference report.

Additionally, the block 280 reads input commands that may be receivedfrom the OA&M processor 108. Generally, such commands may be used toperform ANF module 100 configuration and measurement. In particular, thecommands may be commands that put the ANF module 100 in various modessuch as, for example, a normal mode, a test mode in which built in testequipment is employed or activated, or a bypass mode in which the ANFmodule 100 is completely bypassed. Additionally, commands may be used tochange identifying characteristics of the ANF module 100. For example,commands may be used to change an identification number of the ANFmodule 100, to identify the type of equipment used in the ANF module100, to identify the geographical location of the ANF module 100 or toset the time and date of a local clock within the ANF module 100.Further, commands may be used to control the operation of the ANF module100 by, for example, adding, changing or deleting the narrowbandchannels over which the ANF module 100 is used to scan or to changemanually the threshold at which a signal will be classified as aninterferer. Further, the attack time and the hang time, each of which isdescribed below, may be changed using commands. Additionally, a commandmay be provided to disable the ANF module 100.

After the block 280 has completed execution, the signal processing andinterference identification routine 260 returns control back to the mainroutine 200, which continues execution at the block 208.

As shown in FIG. 14, the interference extraction routine 208 beginsexecution at a block 290, which compares the time duration that aninterferer has been present with a reference time called “duration timeallowed,” which may also be referred to as “attack time.” If theinterferer has been present longer than the attack time, control passesto a block 292. Alternatively, if the interferer has not been presentlonger than the duration time allowed, control passes to a block 296,which is described in further detail below. Essentially, the block 290acts as a hysteresis function that prevents filters from being assignedto temporary interferers immediately as such interferers appear.Typically, the duration time allowed may be on the order of 20milliseconds (ms), which is approximately the frame rate of a CDMAcommunication system. As will be readily appreciated by those havingordinary skill in the art, the frame rate is the rate at which a basestation and a mobile unit exchange data. For example, if the frame rateis 20 ms, the mobile unit will receive a data burst from the basestation every 20 ms. The block 90 accommodates mobile units that are inthe process of initially powering up. As will be appreciated by thosehaving ordinary skill in the art, mobile units initially power up with atransmit power that is near the mobile unit transmit power limit. Afterthe mobile unit that has initially powered up establishes communicationwith a base station, the base station may instruct the mobile unit toreduce its transmit power. As the mobile unit reduces its transmitpower, the mobile unit may cease to be an interference source to a basestation having an ANF module. Accordingly, the block 290 prevents theANF module 100 from assigning a notch module 110, 112 to an interfererthat will disappear on its own within a short period of time.

At the block 292, the microcontroller 106 determines whether there areany notch modules 110, 112 that are presently not used to filter aninterferer. If there is a notch module available, control passes fromthe block 292 to a block 294, which activates an available notch moduleand tunes that notch module to filter the interferer that is present inthe wideband signal from the splitter 24. After the block 294 hascompleted execution, control passes to the block 296, which is describedbelow.

If, however, the block 292 determines that there are no notch modulesavailable, control passes from the block 292 to a block 298, whichdetermines whether the present interferer is stronger than anyinterferer to which a notch module is presently assigned. Essentially,the block 298 prioritizes notch modules so that interferers having thestrongest signal levels are filtered first. If the block 298 determinesthat the present interferer is not stronger than any other interferer towhich a notch module is assigned, control passes from the block 298 tothe block 296.

Alternatively, if the present interferer is stronger than an interfererto which a notch module is assigned, control passes from the block 298to a block 300. The block 300 determines whether the interferer that isweaker than the present interferer passes a hang time test. The hangtime test is used to prevent the ANF module 100 from deassigning a notchmodule 110, 112 from an interferer when the interferer is in a temporaryfading situation. For example, if a mobile unit is generatinginterference and a notch module 110, 112 has been assigned to filterthat interference, when the mobile unit enters a fading situation inwhich the interference level is detected at an ANF module 100 becomeslow, the ANF module 100 does not deassign the notch module being used tofilter the fading interference until the interference has not beenpresent for a time referred to as hang time. Essentially, hang time is ahysteresis function that prevents notch modules from being rapidlydeassigned from interferers that are merely temporarily fading and thatwill return after time has passed. Hang time may be on the order ofmilliseconds of seconds. Accordingly, if the interferer that is weakerthan the present interferer passes hang time, control passes to a block302. Alternatively, if the interferer weaker than the present interfererdoes not pass hang time, the block 300 passes controlled to the block296.

At the block 302, the microcontroller 106 deactivates the notch modulebeing used to filter the weaker interferer and reassigns that same notchmodule to the stronger interferer. After the block 302 has completed thereassignment of the notch module, control passes to the block 296.

At the block 296, the microcontroller 106 rearranges interferers fromlowest level to highest level and assigns notches to the highest levelinterferers. As with the block 298, the block 296 performs prioritizingfunctions to ensure that the strongest interferers are filtered withnotch modules. Additionally, the block 296 may analyze the interferencepattern detected by the ANF module 100 and may assign filters 172-178having various notch widths to filter interferers. For example, if theANF module 100 detects interference on contiguous channels collectivelyhave a bandwidth of 50 KHz, the 50 KHz filter 176 of the notch filterblock 158 may be used to filter such interference, rather than usingfour 15 KHz filters. Such a technique essentially frees up notch filtermodules 110, 112 to filter additional interferers.

After the block 296 has completed execution, control passes to a block304, which updates interference data by sending a list of channels andtheir interference status to a memory (e.g., the memory 118 or 120) thatmay be accessed by the OA&M processor 108. After the block 304 hascompleted execution, the interference extraction routine 208 returnscontrol to the main module 200, which continues execution at the block210.

At the block 210, as shown in FIG. 15, the microcontroller 106determines if a gross failure has occurred in the ANF module 100. Such adetermination may be made by, for example, determining if a voltageoutput from a voltage regulator of the ANF module 100 has an appropriateoutput voltage. Alternatively, gross failures could be determined bytesting to see if each of the notch modules 110, 112 are inoperable. Ifeach of the notch modules is inoperable, it is likely that a grossfailure of the ANF module 100 has occurred. Either way, if a grossfailure has occurred, control passes from the block 320 to a block 322at which point the microcontroller 106 enables the bypass switch 116 ofFIG. 7 to bypass all of the notch modules 110, 112 of the ANF module100, thereby effectively connecting the splitter 24 directly to thewideband receiver 30. After the execution of the block 322, or if theblock 320 determines that a gross failure has not occurred, controlpasses back to the main routine 200, which continues execution at theblock 212. At the block 212, the interference data that was written tothe memory 118 or 120, is passed to the OA&M processor 108.

Having described the functionality of the software that may be executedby the microcontroller 106, attention is now turned to the OA&Mprocessor 108 of FIG. 7. If the blocks shown in FIG. 16 representsoftware functions, instructions embodying the functions may be writtenas routines in a high level language such as, for example, C, or anyother suitable high level language, and may be compiled into a machinereadable format. Alternatively, instructions representative of theblocks may be written in assembly code or in any other suitablelanguage. Such instructions may be stored within the OA&M processor 108or may be stored within the external memory 120 and may be recalledtherefrom for execution by the OA&M controller 108.

In particular, as shown in FIGS. 16A and 16B, which are referred toherein collectively as FIG. 16, a main routine 340 executed by the OA&Mprocessor 108 may begin execution at a block 342, at which the OA&Mprocessor 108 is initializes itself by establishing communication,checking alarm status and performing general housekeeping tasks. At theblock 342, the OA&M processor 108 is initialized and passes control to ablock 344.

At the block 344, the OA&M processor 108 determines whether there is newdata to read from an OA&M buffer (not shown). If the block 344determines that there is new data to read, control passes to a block346, which determines if the new data is valid. If the new data isvalid, control passes from the block 346 to a block 348, which read thedata from the OA&M buffer. Alternatively, if the block 346 determinesthat the new data is not valid, control passes from the block 346 to ablock 350, which resets the OA&M buffer. After the execution of eitherthe block 348 or the block 350, control passes to a block 352, which isdescribed in further detail hereinafter.

Returning to the block 344, if the block 344 determines that there is nonew data to be read, control passes to a block 360, which calculatespower levels of each of the channels scanned by the ANF module 100. TheOA&M processor 108 is able to calculate power levels at the block 360because the data generated as the microcontroller 106 of the ANF module100 scans the various channels is stored in a buffer that may be read bythe OA&M processor 108.

After the power levels have been calculated at the block 360, controlpasses to a block 362, which determines if the any of the calculatedpower levels exceed a predetermined threshold. If the calculated powerlevels do exceed the predetermined threshold, control passes from theblock 362 to a block 364, which tracks the duration and time of theinterferer before passing control to a block 366. Alternatively, if theblock 362 determines that none of the power levels calculated to theblock 360 exceed the predetermined threshold, control passes from theblock 362 directly to the block 366.

The block 366 determines whether the interferer being evaluated waspreviously denoted as an interferer. If the block 366 determines thatthe interferer being evaluated was not previously an interferer, controlpasses to the block 352. Alternatively, the block 366 passes control toa block 368.

At the block 368, the OA&M processor 108 determines whether the presentinterferer was a previous interferer that has disappeared, if so, theOA&M processor 108 passes control to a block 370. Alternatively, if thepresent interferer has not disappeared, control passes from the block368 to a block 372.

At the block 370, the OA&M processor 108 stores the interferer starttime and duration. Such information may be stored within the OA&Mprocessor 108 itself or may be stored within the external memory 120 ofthe OA&M processor 108. After the block 370 has completed execution,control passes to the block 352. At the block 372, the duration of theinterferer is incremented to represent the time that the interferer hasbeen present. After the execution of block 372, control passes to theblock 352.

The block 352 determines whether a command has been received at the OA&Mprocessor 108 from the reporting and control facility. If such a commandhas been received, control passes from the block 352 to a block 380. Atthe block 380, the OA&M processor 108 determines if the command is forthe microcontroller 106 of the ANF module 100, or if the command is forthe OA&M processor 108. If the command is for the microcontroller 106,control passes from the block 380 to a block 382, which sends thecommand to the microcontroller 106. After the execution of the block382, the main routine 340 ends.

Alternatively, if the command received by the OA&M processor 108 is nota command for the microcontroller 106, control passes from the block 380to a block 384, which prepares a response to the command. Responses mayinclude simple acknowledgments or may include responses includingsubstantive data that was requested. Further detail on the block 384 isprovided in conjunction with FIG. 17. After the block 384 has prepared aresponse, a block 386 activates the serial interrupt of the OA&Mprocessor 108 and ends execution of the main routine 340.

Alternatively, if the block 352 determines that a command was notreceived, control passes from the block 352 to a block 390, whichdetermines if the bypass switch 116 of FIG. 7 is closed (i.e., thebypass is on). If the block 390 determines that the bypass is not on,the execution of the main routine 340 ends. Alternatively, if the block390 determines that the bypass is on, control passes from the block 390to a block 392.

At the block 392, the OA&M processor 108 determines whether there was aprior user command to bypass the ANF module 100 using the bypass switch116. If such a user command was made, execution of the main routine 340ends. Alternatively, if there was no prior user command bypass the ANFmodule 100, control passes from the block 392 to a block 394, whichcompares the bypass time to a hold time. If the bypass time exceeds thehold time, which may be, for example, one minute, control passes fromthe block 394 to a block 396.

At the block 396, an alarm is generated by the OA&M processor 108 andsuch an alarm is communicated to a reporting and control facility by,for example, pulling a communication line connected to the reporting andcontrol facility to a 24 volt high state. After the execution of theblock 396, the main routine 340 ends.

Alternatively, if the block 394 determines that the bypass time has notexceeded the hold time, control passes from the block 394 to a block398, which counts down the hold time, thereby bringing the bypass timecloser to the hold time. Eventually, after the block 398 sufficientlydecrements the hold time, the block 394 will determine that the bypasstime does exceed the hold time and pass control to the block 396. Afterthe block 398 has completed execution, the main routine 340 ends.

As shown in FIG. 17, the prepare response routine 384 begins executionat a block 400. At the block 400, the OA&M processor 108 readsinformation that the microcontroller 106 has written into a buffer(e.g., the memory 118 or 120) and calculates the duration of theinterferers that are present, calculates interferer power levels andcalculates the average signal power. This information may be storedlocally within the ANF module 100 or may be reported back to a networkadministrator in real time. Such reporting may be performed wirelessly,over dedicated lines or via an Internet connection. The interferer powerlevels and the average signal power may be used to evaluate the spectralintegrity of a geographic area to detect the presence of any fixedinterferers that may affect base station performance. Additionally, suchinformation may be used to correlate base station performance with theinterference experienced by the base station. After the block 400completes execution, control passes through a block 402.

At the block 402, the OA&M processor 108 adds real time markers to theinformation calculated in the block 400 and stores the reportinformation including the real time markers and the informationcalculated in the block 400. Such information may be stored within theOA&M processor 108 itself or may be stored within the external memory120 of the OA&M processor 108.

After the block 402 has completed execution, control passes to a block404, which determines whether a command has been received by the ANFmodule 100. Such commands would be received from a reporting and controlfacility. If the block 404 determines that no command has been receivedby the OA&M processor 108, control passes from the block 404 back to themain routine 340, which continues execution at the block 386.

Alternatively, if the block 404 determines that a command has beenreceived by the OA&M processor 108, control passes from the block 404 toa block 406, which determines if the received command is a controlcommand that would be used to control the operation of the ANF module100 from a remote location, such as the reporting and control facility.If the block 406 determines that the command received is a controlcommand, the block 406 transfers control to a block 408 which takes theaction prescribed by the command. Commands may include commands that,for example, commands that enable or disable remote control of the ANFmodule 100, or may include any other suitable commands. After theexecution of the block 408, control passes from the prepare responseroutine 384 back to the main routine 340, which then ends execution.

Alternatively, if the block 406 determines that the command received bythe OA&M processor 108 is not a control command, control passes from theblock 406 to a block 410, which determines if the received command is areport command. If the command was not a report command, the block 410passes control back to the main routine 340. Alternatively, if the block410 determines that the received command is a report command, controlpasses from the block 410 to a block 412, which prepares and sends outthe interference report. The interference report may include informationthat shows the parameters of the most recent 200 interferers that weredetected by the ANF module 100 and the information on which themicrocontroller 106 wrote to a memory 118, 120 that the OA&M processor108 accesses to prepare the interference report. The interference reportmay include the frequency number (channel) on which interference wasdetected, the RF level of the interferer, the time the interfererappeared, the duration of the interferer and the wideband signal powerthat was present when the interferer was present.

In addition to the interference report, the OA&M processor 108 mayprepare a number of different reports in addition to the interferencereport. Such additional reports may include: mode reports (report theoperational mode of the ANF module 100), status reports (reports alarmand system faults of the ANF module 100), software and firmware versionreports, header reports (reports base station name, wideband carriercenter frequency, antenna number and base station sector), date reports,time reports, activity reports (reports frequency number, RF level,interferer start time, interferer duration, and wideband channel power)and summary reports.

The interference report may be used for network system diagnosticpurposes including determining when the network administrator should usea narrowband receiver 28 to determine a telephone number that the mobileunit is attempting to contact and, optionally handling the call. Forexample, the reporting and control facility may use the narrowbandreceiver 28 to determine that the user of the mobile unit was dialing911, or any other emergency number, and may, therefore, decide that thenarrowband receiver 28 should be used to handle the emergency call byrouting the output of the narrowband receiver 28 to a telephone network.

Additionally, the interference report may be used to determine when anetwork administrator should control the narrowband receiver 28 toobtain particular information relating to an interferer and retaskingthe interferer by communicating with its base station. For example, thereporting and control facility may use the narrowband receiver 28 todetermine the identity of an interferer, such as a mobile unit, byintercepting the electronic serial number (ESN) of the mobile unit,which is sent when the mobile unit transmits information on thenarrowband channel. Knowing the identity of the interferer, thereporting and control facility may contact infrastructure that iscommunicating with the mobile unit and may request the infrastructure tochange the transmit frequency of the mobile unit (i.e., the frequency ofthe narrowband channel on which the mobile unit is transmitting) or mayrequest the infrastructure to drop communications with the interferingmobile unit all together.

Further, the interference reports may be used by a network administratorto correlate system performance with the information provided in theinterference report. Such correlations could be used to determine theeffectiveness of the ANF module 100 on increasing system capacity.

After the block 412 has completed execution, control passes back to themain routine 340, which continues execution at the block 386.

Referring now to FIG. 18, a data buffer interrupt function 500 isexecuted by the OA&M processor 108 and is used to check for, andindicate the presence of, valid data. The function 500 begins executionat a block 502, which checks for data.

After the execution of the block 502, control passes to a block 504,which checks to see if the data is valid. If the block 504 determinesthat the data is valid, control passes from the block 504 to a block506, which sets a valid data indicator before the function 500 ends.Alternatively, if the block 504 determines that the data is not valid,control passes from the block 504 to a block 508, which sets a not validdata indicator before the function 500 ends.

Numerous modifications and alternative embodiments of the invention willbe apparent to those skilled in the art in view of the foregoingdescription. For example, while the foregoing description specificallyaddressed the concept of eliminating interference from signals on 30 KHznarrowband channels interfering with a 1.25 MHz wideband signal, it willbe readily appreciated that such concepts could be applied to widebandchannels having, for example, 5, 10 or 15 MHz bandwidths or tocontiguous channels that have an aggregate bandwidth of, for example, 5,10 or 15 MHz. To accommodate such wider bandwidths, banks ofdownconverters may be operated in parallel to cover 1.25 MHz block ofthe channel. Accordingly, this description is to be construed asillustrative only and not as limiting to the scope of the invention. Thedetails of the structure may be varied substantially without departingfrom the spirit of the invention, and the exclusive use of allmodifications, which are within the scope of the appended claims, isreserved.

What is claimed is:
 1. A method, comprising: analyzing a wide frequencyband with respect to signal power levels in specified narrow frequencybands; detecting narrow band signal power levels received in thespecified narrow frequency bands; determining an average compositewideband power level from less than all of the narrow band signal powerlevels; determining an adaptive threshold from the average compositewideband power level; detecting narrow band interference according tothe adaptive threshold; and configuring a filter to suppress at least aportion of the detected narrow band interference.
 2. The method of claim1, wherein each of the specified narrow frequency bands has a bandwidththat is smaller than the wide frequency band, and wherein the adaptivethreshold has a power level that exceeds the average composite widebandpower level.
 3. The method of claim 1, wherein the filter selectivelysuppresses at least the portion of the detected narrow bandinterference.
 4. The method of claim 1, wherein the adaptive thresholdis configured for hysteresis.
 5. The method of claim 1, wherein theadaptive threshold comprises more than one threshold.
 6. The method ofclaim 1, wherein the detecting of the narrow band interference accordingto the adaptive threshold comprises detecting a plurality of narrow bandinterferers having power levels that exceed the adaptive threshold. 7.The method of claim 6, wherein the filter comprises a plurality ofsub-filters, and wherein the configuring the filter comprisesconfiguring each of the plurality of sub-filters to suppress at leastthe portion of the plurality of narrow band interferers.
 8. The methodof claim 7, wherein the filter has a variable stop band.
 9. The methodof claim 1, wherein the analyzing of the wide frequency band, thedetecting of the narrow band signal power levels, the determining of theaverage composite wideband power level, the determining of the adaptivethreshold, the detecting of the narrow band interference, and theconfiguring of the filter are performed by a base station.
 10. Themethod of claim 9, wherein the base station is a cellular base station.11. The method of claim 1, comprising repeating the analyzing of thewide frequency band, the detecting of the narrow band signal powerlevels, the determining of the average composite wideband power level,the determining of the adaptive threshold, the detecting of the narrowband interference, and the configuring of the filter to suppressadditional narrow band interference.
 12. The method of claim 1, whereinthe determining of the average composite wideband power level comprisesnot including a subset of the narrow band signal power levels in thedetermination of the average composite wideband power level.
 13. Themethod of claim 12, wherein the subset of the narrow band signal powerlevels have a largest signal strengths in the specified narrow frequencybands.
 14. A device, comprising: a radio frequency receiver; a filter;and a circuit coupled to the radio frequency receiver and the filter,wherein execution of instructions by the circuit cause the circuit toperform operations comprising: causing the radio frequency receiver toscan a wide frequency band; measuring power levels in narrow frequencybands from signals provided by the radio frequency receiver; determiningan average wideband power level from less than all of the power levelsin the narrow frequency bands; determining a threshold from the averagewideband power level; detecting from the signals narrow bandinterference based on the threshold; and configuring the filter tosuppress at least a portion of the detected narrow band interference.15. The device of claim 14, wherein the device is a base station. 16.The device of claim 15, wherein the base station comprises a cellularbase station.
 17. The device of claim 14, wherein the filter has avariable stop band.
 18. The device of claim 14, wherein the circuitfurther performs operations comprising updating the threshold, theaverage wideband power level, or both according to subsequentmeasurements of power levels in the narrow frequency bands.
 19. A memorydevice, comprising instructions, which when executed by a circuit, causethe circuit to perform operations comprising: measuring power levels innarrow frequency bands of signals provided by a radio frequency receiverconfigured to scan radio frequency signals over a wide frequency band;calculating an average wideband power level from less than all of themeasured power levels; determining a threshold from the average widebandpower level, less than all of the measured power levels in the narrowfrequency bands, or both; detecting from the signals narrow bandinterference based on the threshold; and suppressing at least a portionof the detected narrow band interference.
 20. The memory device of claim19, wherein the threshold has a power level that exceeds the averagewideband power level.